The invention relates to an orthodontic bracket, which comprises a body portion and a locking portion, and in the body portion there is an archwire slot for an archwire, and in the orthodontic bracket there is a surface against the tooth and a surface facing away from the tooth. The invention relates also to an arrangement for correcting irregularities of the teeth, which arrangement comprises orthodontic brackets to be attached to the teeth and an archwire to focus force to the orthodontic brackets.
In orthodontics fixed devices and detachable devices are used. Fixed devices are comprised of orthodontic brackets and tubes that are attached to the surface of the tooth generally with glue so that the base of the body of the orthodontic bracket or tube is against the tooth, and archwire, which is attached to the brackets and the ends of the archwire are placed in the tubes. The archwire focuses force to the orthodontic brackets and at the same time to the teeth, with which force the teeth are tried to move to their desired places. The tubes are generally last in the bracket rows at both ends. The orthodontic brackets are generally made of metal. The archwire is generally made of metal and the archwire has some shape to which it attempts to return if it is placed under strain.
There is a slot in the body of the orthodontic bracket, in which the archwire is placed. Generally this slot is angular, the three walls of which are in cross section of the slot substantially perpendicular towards each other. Furthermore in the bracket there are parts with the help of which the archwire is fastened to the slot and parts to which tighteners can be attached to add traction between the brackets, such as for example rubber bands or metal ligature wires. Traditionally the archwire is tied to the slot with binding material by using the tie wings at the upper and lower part of the bracket as the support members of the binding material. Metal or rubber ligature wires or rubber ligatures can be used as binding material. Also brackets in which the archwire is locked in place over by a slidable or rotatable locking arrangement moved over the archwire slot. Also in these brackets tie wings are needed for placing the tighteners.
In FIG. 1 an example is presented of an orthodontic bracket according to prior art. In the orthodontic bracket there is a surface 101 against the tooth and a surface 102 facing away from the tooth. There is a slot 103 in the orthodontic bracket for the archwire. The slot is perpendicular. There are two tie wings 104 which are curved towards the surface of the tooth on both sides of the slot for the archwire to be attached to the slot.
In FIG. 2 there is the orthodontic bracket of FIG. 1 attached to the surface 201 of the tooth and as seen above. The orthodontic bracket is attached generally with glue or a corresponding substance to the tooth. The archwire 202 is placed in the slot 103. The fixing wire 203 holds the archwire in place. The fixing wire runs under the tie wings 104 and over the archwire. The orthodontic brackets are attached usually to several teeth and the archwire is attached to each bracket. When the archwire is attached it is under strain and it focuses force to the orthodontic brackets and through them to the teeth.
Tighteners, which are usually loops made out of elastic material, that cause additional traction can be attached between the orthodontic brackets. These tighteners are attached in the case according to the example to the tie wings 104. Since also the fixing wire 203 of the archwire has to be placed on the tie wings, the orthodontic bracket's profile becomes inevitably high. Also space must be reserved for the placing of fixing wire and possible tighteners, in other words the ends of the tie wings cannot be very close to the surface of the teeth.
In FIG. 3 there is an example of an arrangement for correcting irregularities of the teeth. The arrangement is comprised of orthodontic brackets 301, archwire 302, tighteners 303 and tubes 304. The orthodontic brackets are attached to the teeth 305. Orthodontic brackets are placed in the case according to the example on the buccal side of the teeth, but they can also be placed on the lingual side of the teeth. The archwire is generally attached to all orthodontic brackets. The archwire is under strain and it focuses force to the teeth, which force gradually shifts the teeth towards the desired position or orientation. The ends of the archwire are placed in the so called tubes at the end of the row. Additional traction can be created between the orthodontic brackets with tighteners. The tighteners are attached on the projections of the orthodontic brackets.
At the beginning of the orthodontic treatment usually small archwires with circular cross sections are used to shift the teeth into a row. In most cases the wire is switched at some point of the treatment. At that time an angular archwire can be placed in the slot. If the walls of the angular archwire and the walls of the slot are diverging, the archwire causes with the help of the orthodontic bracket a torque force to the tooth which shifts the root of the tooth. When the upper and lower surfaces of the angular archwire are parallel to the occlusion level, the archwire torques the lower and upper surface of the bracket slot parallel to the occlusion level. When the surfaces of the bracket slot and the tooth are in the predetermined angle in relation to each other, the surface of the tooth can be set to a desired orientation in relation to the occlusion level.
The brackets can be attached to all of the teeth. Generally a different type of bracket is needed for each tooth because the torque angle of the archwire slot of each bracket is different for each tooth depending on which position the tooth is desired to be after the treatment is over. Also the width and thickness as well as the shape of the base of the bracket varies according to the teeth. The brackets can also be attached on the front and rear surfaces of the teeth, whereupon the forming and other variables of the base of the orthodontic bracket are also different.
A particular challenge for the brackets used on the rear surfaces of the teeth is that the brackets must have be as low profiled as possible to fit between the upper and lower teeth in the region of the incisors and obstruct as little as possible the tongue. Furthermore the placement of the archwire and the tighteners should be simple, because working on the lingual surfaces of the teeth is difficult.
An orthodontic bracket is known form patent publication U.S. Pat. No. 6,942,483 in which the archwire is held in place by a closing spring structure. The assembly becomes quite high profiled. In this solution there needs to also be tie wings in the orthodontic bracket for tighteners.
From patent publication U.S. Pat. No. 7,214,057 an orthodontic bracket is known, in which the archwire is held in its place by a curved plate arrangement. There is an opening at the lower part of the orthodontic bracket in which the elongated portion of the plate arrangement is placed and the curved portion of the plate arrangement sits over the orthodontic bracket, in which this curved portion keeps the archwire in the slot. Using the curved plate arrangement and the tie wings makes the orthodontic bracket high profiled, whereby it readily disturbs the user and the archwire is left quite far from the surface of the tooth.
An orthodontic bracket is known from patent publication U.S. Pat. No. 7,396,230 in which the archwire is held in place by a flexible cover fixed to the orthodontic bracket. The cover is fixed from its one end to the surface of the orthodontic bracket and it can be flexibly deformed over the surface of the orthodontic bracket that faces away from the tooth and the protrusion on the cover attaches on the groove in the orthodontic bracket and the cover thus keeps the archwire in place in either said groove or in a slot meant for the archwire. Further there is a hook in the orthodontic bracket for additional fasteners. Orthodontic bracket structure according to the publication makes it high profiled, which impedes the mounting and use for example on the lingual surfaces of the teeth.